Witnesses to the crash have told smh.com.au the group of about up to 60 professional cyclists were riding south on Southern Cross Drive, just south of Dacey Avenue, Mascot about 6.30am when a driver, agitated with being held up, accelerated in front of the pack and then slammed on his brakes.

One of the group said the motorists was "worrying" the rear of the pack, then overtook, pulled in front and slammed on his brakes, giving the riders no time to stop.

The resulting smash forced a semitrailer to lock up, jackknife and screech to a halt behind the cyclists while cars had to swerve to avoid them.

"Everyone's slammed into each other ... there were broken bikes - wheels busted and wheels snapped - and people lying on the road."

"Three female cyclists took the brunt of the accident, careering into the back of the braking vehicle, several of them being thrown into the air landing on the boot and roof of the car."

The best part:

It is understood (the authorities) know who the driver of the car is, and are attempting to contact him now.

It is expected he will be charged, including with failing to stop at the scene of an accident and negligent or dangerous driving.

There was no doubt the driver of the dark blue Ford Falcon - described by other witnesses as in his 30s with a female passenger - had done it deliberately, she said.